Gas turbine engine thrust reversers

ABSTRACT

Aircraft gas turbine engine duct blocker doors are mounted so as to move across the duct in a manner which causes fluid pressures to combine with door mounting structure reaction loads so as to produce a resultant force on the doors which, up to a given point in aircraft flight conditions, the resultant force tries to stop the doors from moving across the duct and, beyond said point, helps the doors to move across the duct, thereby providing a fail/safe operation of the doors during given aircraft flight conditions.

United States Patent Britt et al.

GAS TURBINE ENGINE THRUST REVERSERS Inventors: Jack Britt, Ambergate;Leonard John Rodgers, Spondon, both of England Assignee:

I-Ier Britannic Majesty 's Government of the United Kingdom of GreatBritain and Northern Ireland, Whitehall, London, England Filed: Oct. 18,1971 Appl. No.: 190,354

Foreign Application Priority Data Oct. 20, 1970 Great Britain 48662/70US. Cl. 239/265.29 Int. Cl. B64c 15/04 Field of Search 239/265.27,265.29,

The Secretary of State for Defence, in

[45] Aug. 28, 1973 [56] References Cited UNITED STATES PATENTS 3,511,0555/1970 Timms 239/2652) 3,608,314 9/1971 239/26529 3,500,646 3/1970 Homet al. 239/265.29 3,568,931 3/1971 Mortlock et al. 239/2652) 3,603,0909/1971 Billinger et al. 239/265.29

Primary ExaminerLloyd L. King Attorney-Cushman, Darby & Cushman [5 7]ABSTRACT Aircraft gas turbine engine duct blocker doors are mounted soas to move across the duct in a manner which causes fluid pressures tocombine with door mounting structure reaction loads so as to produce aresultant force on the doors which, up to a given point in aircraftflight conditions, the resultant force tries to stop the doors frommoving across the duct and, beyond said point, helps the doors to moveacross the duct, thereby providing a fail/safe operation of the doorsduring given aircraft flight conditions.

7 Claims, 8 Drawing Figures Patented Aug. 28, 1973 3,754,708

4 Sheets-Sheet 1 Patented Aug. 28,1973

4 Sheets-Sheet 2 Patented Aug. 28, 1973 3,754,708

4 Sheets-Sheet 5 FIG 6 Patented Aug. 28,1973 3,754,708

4 Sheets-Sheet 4.

1 GAS TURBINE ENGINE TIIRUST REVERSERS This invention concerns gasturbine engine thrust reversers.

It has, in the past, proved difficult to provide gas turbine engineswith thrust reverser equipment which will, in the event of failure ofthe reverser actuating means, move to a position which will least impairthe thrust requirements from the engine at the time of failure. Forexample if the engine is mounted on an aircraft for propulsion thereofand the aircraft is making a landing approach and the thrust reversermeans is being utilized to control the total forward thrust of theengine, as is described in the copending U. S. application Ser. No.123,753 filed Mar. 12, 1971., should the reverser actuating means fail,it is imperative that the blocker doors which form part of the reverserequipment, return to their non-operative positive wherein they form acontinuation of the fluid flow duct wall, thus so as to be able toobtain full thrust from the engine to keep the aircraft flying. If theaircraft is about to touch down or has touched down and full reversethrust is requiredbut the actuating mechanism fails, then the blockerflaps must be able at this point in time, to swing fully across saidduct so as to block the fluid flow and so brake the aircraft.

It is therefore an object of this invention to provide thrust reverserequipment which incorporates fail/safe features for each of theconditions stated hereinbefore.

Accordingly the present invention comprises a gas turbine engine havinga fluid flow duct defined by at least one wall, said wall includingwithin its length a plurality of peripherally spaced fluid flow blockerdoors which when non-operative block respective apertures in said walland which are articulately linked by their mid portions to fixedstructure upstream of said apertures and movably mounted at theirdownstream ends in mounting means, mounted on fixed structure downstreamof said apertures, and blocker door actuating means, the arrangementbeing such that actuation of said actuation means causes said doors tomove across the fluid flow at an angle or series of angles to thedirection of fluid flow such that the combination of fluid pressure onthe outer surfaces thereof and mounting means reaction forces on thedoor mounting therein, provides a resultant force which tends to returnthe doors to their in-operative position, until such time as engineresultant thrust is zero whereupon the direction of the resultant forcereverses.

Preferably the mounting means comprises a cam track.

Alternatively the mounting means could comprise links.

Preferably initial direction of movement of the blocker doors towardsthe fluid flow blocking position is substantially radially inwardstowards the duct axis, the doors being maintained substantially paralleltherewith, thus permitting fluid at duct pressure to flow both sides ofeach of said blocker doors.

Preferably the actuating means comprises a plurality of chains spaced inpairs between adjacent blocker doors and supported on sprocket wheels.

Preferably each chain is connected to the downstream end of eachrespective blocker door by an extension through the cam tracks of one ofthe pins which link the tension plates of the chain.

Preferably several consecutive pins ofeach chain are also extended, butin the opposite direction to said one pin and located in a further camtrack similar in profile to the first cam track such that a portion ofthe chain is supported on both sides and caused to follow a preselectedcurved path defined by the cam tracks when moving between at least twoadjacent sprocket wheels.

Preferably the chains are connected for driving in pairs.

Preferably the connection is obtained by a yoke, each end of the yokebeing attached to a pin of a respective chain, the yoke being adaptedfor traversing axially of the duct.

Preferably the adaptation comprises attaching the yoke means to the nutof a ball screw and nut assembly such that rotation of the screwtraverses the nut and yoke means together axially of the duct, thusdriving the pair of chains.

Alternatively each chain may be gear driven.

The invention will now be described by way of example only and withreference to the accompanying drawings in which:

FIG. 1 is a diagrammatic view of a gas turbine engine.

FIG. 2 is a general axis diagrammatic section through the fan cowl ofthe gas turbine engine of FIG. 1.

FIG. 3 is an enlarge axial section on line 2-2 of FIG.

FIG. 4 is a pictorial part view of a fan cowl structure. FIG. 5 is apart sectional view on line 55 of FIG. 3.

FIG. 6 is an enlarged part view of an idler sprocket wheel.

FIG. 7 is a developed part view of a pair of adjacent blocker doors.

FIG. 8 is a pictorial view ofa chain and its associated drive mechanism.

In FIG. 1 a gas turbine engine 10 includes a ducted fan stage 12, theduct 14 being defined by the engine casing 16 and fan cowl 18.

Fan cowl 18 contains thrust deflecting equipment 20 whereby duringoperation of the engine air flowing through duct 14 may be partially ortotally deflected through an aperture in cowl 18 instead of beingejected from the nozzle 22.

The thrust deflecting apparatus comprises a plurality of blocker doors24 spaced peripherally of the outer wall of duct 14 so that when notoperative, the doors form smooth continuations of the outer wall of theduct as can be seen in FIG. 3.

Adjacent doors are spearated by a rigid strut 26 which is hollow andcontains blocker door actuating mechanisms 28 (FIG. 5). This mechanismextends downstream into fixed structure which forms part of thedownstream portion of cowl l8 and said mechanism preferably comprises apair of sprocket chains 30, seen best in FIGS. 6, 7 and 8, eachsupported by four idler double sprocket wheels 32, 33, 34 and 35 mountedfor rotation about fixed axes in the fixed structure. Double sprocketwheels having the chain therebetween are used in order to centralise thetensile loads felt by the chain during operation of the mechanism. Theblocker doors are connected at their downstream ends, by a lug mountedpin or roller 36, which extends through a fixed cam track 40 and formsone pin of a respective chain. This is best seen in FIG. 6. Theparticular pin 36 is further extended so that its end remote from theblocker door lug, at least during some part of the operation of themechanism, is located in a further cam track 42 similar in shape to camtrack 40. The cam tracks are aligned with each other. One set of foursprocket wheels 32, 33, 34 and 35 lies in a plane centrally of the twocam tracks. Several of the pins 44 which connect the links of eachsprocket chain are also extended so that they at some part of theoperation, locate in cam track 42, the reason being that the upper partsof the cam tracks are curved and the chain must be forced to follow thecurve rather than a straight line between wheels 34 and 35. Any sideloads experienced by pins 44 whilst following the curve thus, areabsorbed by the cam tracks and the structure to which the cam tracks arefixed.

In the particular example, each pair of chains is driven by a ball screwand nut mechanism 46 which lies between the chains, a yoke 48 beingattached to the nut and each end 50, S2 of the yoke in turn beingadapted to act on a link pin in a respective chain.

Each blocker door 24 is further connected to fixed structure by a link54 of which that end remote from the door is pivotally connected to asolid ring 56 at the upstream end of the aperture in cowl 18.

OPERATION The gas turbine engine described herein is designed formounting on an aircraft and during normal cruise flight of the aircraft,blocker doors 24 will lie in known manner along the outer wall of duct14. When the aircraft starts its landing run, the pilot will control theengine in the manner described in the co-pending application Ser. No.123,753. Briefly, that is, although descending, he will set the enginecontrols at take off thrust, but will then operate his thrust reversercontrols so as to open and close, in a controlled manner, the blockerdoors 24 and other external aperture closure means (not shown) so as tospoil the take off thrust, the overall result being that the aircraftwill reduce forward speed and so continue to descend. During thedescent, the blocker doors must never move fully across the duct 14 forif this happened, allforward thrust would be spoiled and the aircraftforward speed would dramatically reduce. This could happen if theactuating mechanism of the blocker doors fails, the result being thatthe doors would be moved by duct air pressure to a duct blockingposition. However, the mounting of doors 24 in cam track 40 and by link54 ensures by virture of the shape of cam track 40 that each door ismoved in such a manner that until the door reaches a position where theresultant thrust produced by the engine is zero, (that is, reversethrust equals forward thrust) the resultant of the fluid loads on thedoor produces a force on the actuating mechanism in a direction such asto return the door to its non-operative, i.e. full forward thrustposition.

As described in the co-pending application Ser. No. l23,753 the fullreverse thrust will not be deliberately selected until touchdown orimmediately before touchdown whereupon the blocker doors will move pastthe position of engine zero resultant thrust towards full reverse thrustand the direction of the resultant force exerted on the actuatormechanisms will reverse thus holding the doors in the full duct blockingposition, so if actuator failure occurs at this stage, aircraft brakingwill still be achieved as is desirable.

The actual movements of the blocker doors are attained by the pilotrotating the ball screws 46 by flexible drives 62 so that each yoke 48moves axially of the duct in the direction of arrow A. Each chain 30 isthus caused to move around sprocket wheels 32, 33, 34 and 35 and in sodoing moves pin 36 which, being located in cam track 40, at position 65has first to move towards the duct axis. This movement in effect, cracksopen the seal around the blocker doors edges and permits air at ductpressure to enter the aperture. This reduces but does not equalise thepressure difference across the blocker doors inner and outer sides 58and 60 respectively. Thus operating loads on the actuating mechanism arereduced but not obviated. The blocker doors are, at this point,approximately in a position as indicated at 64 in FIG. 2 and theirrespective pins 36 are in a position in the cam tracks indicated at 66.When the doors are in a position 57 their respective pins are in the camtrack at 68 and, as stated, it is while pins 36 are in any positionbetween a non-operative position 65 and position 68 that duct airpressures will endeavour to return the doors to the non-operativeposition thus providing the desirable fail/safe feature for when theaircraft is making its landing approach.

Arrow B in FIG. 8 clearly slows that pins 36 are forced to follow by camtracks 40 and 42 as is also each chain 30.

As an alternative to the ball screw the chain may of course, be geardriven, gears being shown in chain dotted lines at 72 and 74. Gears 72could be flexibly driven and transmit the drive via gears 74 to sprocketwheels 32 and thus chain 30. We claim:

1. In a gas turbine engine power plant:

a casing defining a fluid flow duct for thrust producing fluid, saidcasing having an air intake at its upstream end, a propulsion nozzle atits downstream end and at least one wall with at least one aperturetherein;

thrust reverser means carried within said wall and comprising aplurality of perpherially spaced fluid flow blocker doors;

mounting means for said blocker doors, said mounting means includinglinks each of which is pivotally connected at one end to said casingupstream of said apertures and at the other end to a substantially midportion of a respective one of said doors, and cam means connectingdownstream ends of said doors to said casing downstream of saidapertures, said cam means causing movement of the downstream end of saiddoors in a configurated curved path when said links are pivoted abouttheir upstream ends to provide a first portion of travel of said blockerdoors across said duct from an inoperative position blocking saidapertures, said movement during said first portion of travel causingfluid pressure on said blocker doors and reaction forces on said blockerdoors to cause a resultant force urging return of said blocker doorstoward said inoperative position, and a second portion of travel of saiddoors to a fully operative position where said blocker doors block saidduct, said second portion of travel cuasing a second resultant force onsaid doors reverse of said first-mentioned resultant force and urgingmovement of said doors toward blocking position; and

moving means to selectively move said doors between said fullyinoperative position to said fully operative position with at least oneintermediate position partially across said duct to reverse a fractionof the thrust producing fluid, said at least one intermediate positionbeing in said first portion of travel and having the resultant force onsaid blocker doors urging them to the fully inoperative position.

2. A gas turbine engine as claimed in claim 1 wherein said cam meanscomprises pins each having one end attached to the downstream end ofrespective blocker doors and passing through respective slots formedinto cam tracks mounted in said casing downstream of said apertures, theother end of each said pin being fixed to said blocker door movingmeans.

3. A gas turbine engine as claimed in claim 2 wherein said blocker doormoving means comprises a plurality of endless sprocket chains supportedon sprocket wheels and driven by driving means.

4. A gas turbine engine as claimed in claim 3 wherein said moving meanscomprises a yoke mounted on a ball screw and having two ends, each ofwhich is forced into a pin which locates in a respective sprocket chain,the ball screw being rotatable so that, on rotation thereof, said yoketraverses the ball screw length and causes said sprocket chain to move.

5. A gas turbine engine as claimed in claim 3 wherein each said sprocketchain has a plurality of pins which are extended lengthwise so as tolocate in respective cam tracks in the fixed structure downstream of theapertures so that when said sprocket chains are driven they are forcedto move in the path of their respective cam track.

6. A gas turbine engine as claimed in claim 3 wherein said moving meanscomprises gear chains which are drivingly connected to said sprocketwheels, driving of which in turn drives respective sprocket chains.

7. A gas turbine engine as claimed in claim 3 wherein the moving meansare actuated via flexible drive couplings.

1. In a gas turbine engine power plant: a casing defining a fluid flowduct for thrust producing fluid, said casing having an air intake at itsupstream end, a propulsion nozzle at its downstream end and at least onewall with at least one aperture therein; thrust reverser means carriedwithin said wall and comprising a plurality of perpherially spaced fluidflow blocker doors; mounting means for said blocker doors, said mountingmeans including links each of which is pivotally connected at one end tosaid casing upstream of said apertures and at the other end to asubstantially mid portion of a respective one of said doors, and cammeans connecting downstream ends of said doors to said casing downstreamof said apertures, said cam means causing movement of the downstream endof said doors in a configurated curved path when said links are pivotedabout their upstream ends to provide a first portion of travel of saidblocker doors across said duct from an inoperative position blockingsaid apertures, said movement during said first portion of travelcausing fluid pressure on said blocker doors and reaction forces on saidblocker doors to cause a resultant force urging return of said blockerdoors toward said inoperative position, and a second portion of travelof said doors to a fully operative position where said blocker doorsblock said duct, said second portion of travel cuasing a secondresultant force on said doors reverse of said first-mentioned resultantforce and urging movement of said doors toward blocking position; andmoving means to selectively move said doors between said fullyinoperative position to said fully operative position with at least oneintermediate position partially across said duct to reverse a fractionof the thrust producing fluid, said at least one intermediate positionbeing in said first portion of travel and having the resultant force onsaid blocker doors urging them to the fully inoperative position.
 2. Agas turbine engine as claimed in claim 1 wherein said cam meanscomprises pins each having one end attached to the downstream end ofrespective blocker doors and passing through respective slots formedinto cam tracks mounted in said casing downstream of said apertures, theother end of each said pin being fixed to said blocker door movingmeans.
 3. A gas turbine engine as claimed in claim 2 wherein saidblocker door moving means comprises a plurality of endless sprocketchains supported on sprocket wheels and driven by driving means.
 4. Agas turbine engine as claimed in claim 3 wherein said moving meanscomprises a yoke mounted on a ball screw and having two ends, each ofwhich is forced into a pin which locates in a respective sprocket chain,the ball screw being rotatable so that, on rotation thereof, said yoketraverses the ball screw length and causes said sprocket chain to move.5. A gas turbine engine as claimed in claim 3 wherein each said sprocketchain has a plurality of pins which are extended lengthwise so as tolocate in respective cam tracks in the fixed structure downstream of theapertures so that when said sprocket chains are driven they are forcedto move in the path of their respective cam track.
 6. A gas turbineengine as claImed in claim 3 wherein said moving means comprises gearchains which are drivingly connected to said sprocket wheels, driving ofwhich in turn drives respective sprocket chains.
 7. A gas turbine engineas claimed in claim 3 wherein the moving means are actuated via flexibledrive couplings.